Electrochemical methods selective measuring techniques

Electrochemical methods of analysis have seen wide application as in vivo biosensors. Several features of electroanalytical methods have enhanced their utility in these applications. Electrochemical techniques show sufficient sensitivity and selectivity that in many instances they can be used directly to measure chemical activity. In addition, the probes can be miniaturized so the measurements cause minimum trauma to the tissue. 

The failures by SCC of welded Type 304 piping exposed to water at 289 C with 0.2-8 ppm of oxygen on boiling water nuclear power plants created a demand for a nondestructive method for detecting quantitatively the degrees of sensitization in these pipes. A nondestructive method was needed so that measurements could be made directly on the heat-affected zones of pipes on the plants. For this purpose, Clarke et al. [20] selected and applied the electrochemical potentiokinetic reactivation (EPR) technique. A cell was designed that could be attached to pipes. 

When working with complicated matrices (biological samples or food products), the selectivity of electrochemical methods (ED) can usually be increased if they are combined with effective separation techniques, e.g. capillary electrophoresis and liquid chromatography (Rychlik 2011 Trojanowicz 2011). In separation science, electrochemical detection is used to detect and measure response analytes in flowing streams after separation by HPLC or capillary electrophoresis (Trojanowicz 2011). The former was introduced in the mid-20th century and is still an actively developing analytical technique. Employment of a new generation of columns, new detector types, new software and the... 

Electrochemical methods appear to have distinct advantages in the study of cement hydration. Methods involving potential measurement (including pH, zeta potential, and selected ion potential), conductivity measurement, and a.c. impedance measurement provide useful information related to both ion concentration of pore solution and microstructural change in hydrating cement paste. The early hydration and setting behavior of OPC-CAC and OPC-Hydrated-CAC paste systems can be determined using these techniques. 

The ionic conductivity of a solvent is of critical importance in its selection for an electrochemical application. There are a variety of DC and AC methods available for the measurement of ionic conductivity. In the case of ionic liquids, however, the vast majority of data in the literature have been collected by one of two AC techniques the impedance bridge method or the complex impedance method [40]. Both of these methods employ simple two-electrode cells to measure the impedance of the ionic liquid (Z). This impedance arises from resistive (R) and capacitive contributions (C), and can be described by Equation (3.6-1) ... 

---